Vehicles may use an engine drive system to drive various features in an internal combustion engine. For example, a typical engine drive system for a dual overhead camshaft arrangement includes a timing belt that engages various sprockets to rotate both camshafts and a crankshaft rotate.
For example, U.S. Pat. No. 4,674,452 describes a camshaft driving system for a dual overhead cam engine. The system includes a chain that engages a crankshaft and an intake camshaft. Further, the intake camshaft includes a gear that meshes with an exhaust camshaft gear such that an exhaust camshaft is driven in synchronization with the intake camshaft.
The inventors herein have recognized various issues with the above system. In particular, engaging toothed gears to synchronize the rotation of the camshafts also causes center distance limitations due to noise, vibration, and harshness (NVH) constraints and package constraints.
As such, one example approach to address the above issues is to couple the camshafts with a coupling device. In this way, it is possible to indirectly couple the camshafts, while reducing timing band load.
Specifically, in one embodiment, the coupling device engages a first camshaft via a drive pin and a second camshaft via a driven pin such that a position of the first camshaft is mirrored from a position of the second camshaft. This configuration enables the camshafts to rotate in opposing directions without directly engaging the camshafts with toothed sprockets. In this way, it is possible to engage only one drive camshaft with a timing band and the drive camshaft indirectly drives a driven camshaft that is not engaged with the timing band. Further, by rotating the camshafts in opposing directions, it is possible to take advantage of torque cancellation. As such, torque cancellation can reduce the timing band load resulting in improved durability, performance and fuel economy.
Note that various bands may be used, such as timing chain, a timing belt, or various other types of elastic and/or inelastic flexible bands. Further, the band may mate to toothed or un-toothed pulleys on the various shafts. Further still, additional bands may also be used, if desired.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.